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permaculture writes "The Register describes the difficulty of mixing up a batch of liquid explosives on a plane. Further, it opines that such a plot might work in a Hollywood film, but not in the real world. Liquid explosives were used for the 7/7 London bombings in 2005, according to the official account — or not, as now seems more likely."
This story selected and edited by LinuxWorld editor for the day Saied Pinto.

The "Mark II" "microbombs" had Casio digital watches as the timers, stabilizers that looked like cotton wool balls, and an undetectable nitroglycerin as the explosive. Other ingredients included glycerin, nitrate, sulfuric acid, and minute concentrations of nitrobenzene, silver azide (silver trinitride), and liquid acetone. Two 9-volt batteries in each bomb were used as a power source. The batteries would be connected to light bulb filaments that would detonate the bomb. Murad and Yousef wired an SCR as the switch to trigger the filaments to detonate the bomb. There was an external socket hidden when the wires were pushed under the watch base as the bomber would wear it. The alteration was so small that the watch could still be worn in a normal manner. [1] [5] [7]Yousef got batteries past airport security during his December 11 test bombing of Philippine Airlines Flight 434 by hiding them in hollowed-out heels of his shoes. Yousef smuggled the nitroglycerin on board by putting it inside a contact lens solution bottle.The density of the explosive cocktail would be about 1.3.

I was shocked to hear the media talking about the possibility of bring nitroglycerin onto an airplane. The entire reason that dynamite was invented is because the liquid is horribly volitile. Some people have speculated that the terrorists were not attempting a large scale explosion as CNN and Fox News would have you believe. Instead they were waiting until the plane was in the middle of the Atlantic and starting a fairly large fire. There are many substances that can create a dangerous fire on an airplane in the middle of the ocean at 30,000 feet. There is no need for a Holywood style explosion at all. I am being intentionally vague in this post, but three men with drink containers full of certain substances starting three fires at three different parts of the plane would be extremely difficult to control, especially considering the lack of fire surpression systems in the passenger cabin. I am not a firefighter (rookie EMT and will be training to be a rescuer) but I cannot imagine trying to put out three fires with the 1-2 fire extingueshers available.

The first World Trade Center bombing and OK City show that everyday chamicals can be combined with horrific results. In those situations, however, there were truckloads of the two ingredients. I agree in part with TFA that it would be hard to perform an explosion the size of Pan-Am 103's with liquids, but that is not necesary.

Bruce Schneier linked to another post [schneier.com] which had an interesting take by a chemist in a graduate program. He describes details of the chemicals involved and what it would take to detonate them effectively onboard a plane.

The summary: improvised explosives involve pretty nasty stuff that you'd be hard pressed to mix in an airplane lavatory without killing yourself in the process.

That reinforces my main take on this: the creator of the article has this silly preconceived notion that "murderous" implies "stupid".

First, you've got to get adequately concentrated hydrogen peroxide. This is hard to come by, so a large quantity of the three per cent solution sold in pharmacies might have to be concentrated by boiling off the water. Only this is risky, and can lead to mission failure by means of burning down your makeshift lab before a single infidel has been harmed.

Nope. You can distill H2O2, but not through boiling; boiling breaks it down faster than it will concentrate it. You can do it through creating a partial vaccuum and using lower temperatures.

Besides, it's not like concentrated H2O2 is hard to come by.

Certainly, if we can imagine a group of jihadists smuggling the necessary chemicals and equipment on board, and cooking up TATP in the lavatory, then we've passed from the realm of action blockbusters to that of situation comedy.

And I've seen the mythbusters make a lethal paper crossbow out of newspaper and a lunch tray, as well as eat through an inch thick steel bar with a DC transformer and salsa. Sure, they took their time, but once you've done it once, how hard is it to recreate? You'd be surprised what desperate people who have time to practice beforehand can accomplish. Just because they're "murderous" doesn't mean that they're stupid or uncreative.

Perry Metzger wrote an excellent post [interesting-people.org] to the interesting-people mailing list last Friday. He goes into more detail than the Register article does, offers first-hand information, and packs in more irony and sarcasm besides.

The "Mark II" "microbombs" had Casio digital watches as the timers, stabilizers that looked like cotton wool balls, and an undetectable nitroglycerin as the explosive. Other ingredients included glycerin, nitrate, sulfuric acid, and minute concentrations of nitrobenzene, silver azide (silver trinitride), and liquid acetone. Two 9-volt batteries in each bomb were used as a power source. The batteries would be connected to light bulb filaments that would detonate the bomb. Murad and Yousef wired an SCR as the switch to trigger the filaments to detonate the bomb. There was an external socket hidden when the wires were pushed under the watch base as the bomber would wear it. The alteration was so small that the watch could still be worn in a normal manner. [1] [5] [7]

Yousef got batteries past airport security during his December 11 test bombing of Philippine Airlines Flight 434 by hiding them in hollowed-out heels of his shoes. Yousef smuggled the nitroglycerin on board by putting it inside a contact lens solution bottle.

Does anyone else think that these terrorists' true purpose is not to kill the passengers on a few planes but to inconvenience travellers for years to come?

Their immediate goal is to kill as many infidels as possible, with the final objective of wiping out the US and Israel. It's their mission statement, they make no effort to hide it and anyone who thinks otherwise might as well believe in unicorns.

Not quite sure what your point was, but the idea of opening an airplane door in mid-flight has been thoroughly debunked. For example, see Patrick Smith's Salon Article [salon.com] on the subject (mind-bending advertisements or oppressive money-grubbing subscription may be required). In short, you can't open the door because there's a lot of air pressure holding it shut. From the cited article,

At a typical cruising altitude, as many as 8 pounds of pressure are pushing against every square inch of interior fuselage. That's 1,152 pounds of weight against each square foot of door. Flying at low altitudes, where cabin-pressure levels are lower, even a differential of 2 pounds per square inch is still more than anyone can displace -- even after six cups of coffee and the frustration that comes with sitting behind a shrieking infant for five hours.

Of course, if you don't believe him you can try it for yourself. Remember to pack a hydraulic jack in your carry-on.

Yeh, I think the risk is fire also. Swimming pool chemicals and nail polish remover could do it. Chemical fires are hard to control. A single fire in a vital part of an aircraft it could be catastrophic.

The "Mark II" "microbombs" had Casio digital watches as the timers, stabilizers that looked like cotton wool balls, and an undetectable nitroglycerin as the explosive. Other ingredients included glycerin, nitrate, sulfuric acid, and minute concentrations of nitrobenzene, silver azide (silver trinitride), and liquid acetone. Two 9-volt batteries in each bomb were used as a power source. The batteries would be connected to light bulb filaments that would detonate the bomb. Murad and Yousef wired an SCR as the switch to trigger the filaments to detonate the bomb. There was an external socket hidden when the wires were pushed under the watch base as the bomber would wear it. The alteration was so small that the watch could still be worn in a normal manner.

There's reality-based experience that says cabin de-pressurization won't have anything like the effect you describe. Doesn't anyone remember Aloha 243 [aloha.net]? The top of the plane peeled right off (not just a wussy little window blow-out) at altitude. There was one fatality, a flight attendant who wasn't strapped in. The pilots landed the plane safely.

As for mixing the explosives being "certainly possible" I think you should look at the Perry Metzger article [interesting-people.org] I've also cited elsewhere.

1. Airplane cabins are full of pressurized and highly filtered air. It's (comparatively) safe to work with chlorine gas in a chemistry laboratory because you're working under a hood that takes the poison out of the atmosphere. The same general effect, though not as efficient, would take place inside an airplane cabin. And besides, there's oxygen masks handy.

2. Should every passenger on a plane fall dead of chlorine gas poisoning, it isn't going to "fall out of the sky". It will continue on its autopilot trajectory until it runs out of fuel. The plane that golfer Payne Stewart died on, for example, continued flying for four hours after the passengers were incapacitated. That's too much unpredictability, too much time for the National Guard to shoot the plane down in an unpopulated area.

Also, the difference between 1 atmosphere of pressure (i.e. ground level) and some fraction of an atmosphere (at cruising altitude) is an order of magnitude or so smaller than the difference between ground level and the bottom of the ocean.

Who would have believed that before it happened? Who wouldn't have said that someone had been "watching a few too many Hollywood movies"?

Planes have been hijacked before 9/11, so it's not really that unbelieveable that someone couldn't accomplish the same thing. Learning how to fly isn't really that difficult, and obviously people do it all the time. The most un-intuitive thing about 9/11 was simply that a plane flown into a building could collapse it. That's something only an expert could have predicted. The difference here is that we're getting the information from an expert in the explosive in question. It's pretty obvious from reading the article that making this explosive onboard a plane is difficult no matter how much training you have. If you discount what experts in the field have to say, what isn't "to far fetched"?

Not only is this plan feasible, but a terrorist had already detonated such a device on board an aircraft. In 1995 Philippines Airlines Flight 434 [wikipedia.org] was the target of a bomb left by al-Qaeda terrorist Ramzi Youssef on an earlier leg of the flight. The bomb cut Japanese businessman Haruki Ikegami in half, and ripped through the passenger compartment into the cargo hold. The aircraft lost primary and backup hydraulic controls and had to be flown in via throttles -- a difficult and dangerous maneuver.

Not only that, but the bomb that Youssef left on board that flight was one tenth the power of the bombs he intended to detonate as part of Operation Bojinka. The argument that such a weapon is not feasible is itself more FUD. It is quite possible, and it has been done before. Al-Qaeda operatives are trained in explosives, and they knew exactly what was doing.

Yes, there's a good chance of killing yourself while mixing such a bomb, but I rather doubt that any of the plotters of this attack had any qualms about killing themselves in the process.

If you actually read TFA you'll see the low-powered bomb was as intended as a test, and he planned to use bombs 10x as powerful as that for a major terrorist attack on 11 airliners over the Pacific ocean. Sound familiar?

Underestimating the determination and ingenuity of anyone is a terrible mistake. However, in this case, the terrorists' ingenuity may be at odds with the laws of chemistry. Judging from what I've read through all of the chemists' commentaries in the article and comments, it seems like the liquid based attacks mentioned in the media cannot be carried out regardless of the determination of the terrorists involved.

Actually, their goal is world domination under their hardline view of Islam.

Believe it or not Osama's goals were more secular than religeous.

After he returned from Afghanistan he was sort of a semi-hero in his home country of Saudi Arabia. When Saddam invaded Kutwait in 91, Osama personally offered King Saudi access to Al Queda's 100,000 volunteers and his personal fortune to fight off Saddam from a Saudi invasion.

But... The King's delegation (Osama wasn't allowed to talk to the royal family himself) laughed at Osama's offer because Saddam had over 1,000,000 troops and they were well armed at that.

Then King Saudi invited the American to be based in Saudi and attack an attack on Iraq. This infuriated Osama because no only was his offer rebuffed, but infidels were on holy ground. At that moment he swore revenge and packed his bags and moved to Sudan.

Later... Osama assisted the muslims in Somalia to drive out the Americans. His support was negliable and some say didn't really help as much as he said he did.

The problem with this was that Osama mistakenly thought that if you killed a few Americans they would run with their tails behind their legs because they had no stomach for fighting.

So he mistakenly went about and concocted 9/11 thinking if he brought the fight to their home land the Americans would give in and leave Saudi Arabia.

Of course we know that he was horribly mistaken and would have done better attacking military targets in Saudi Arabia, but that is neither here nor there but there are very secular reasons or at least political reasons that the terrorists do what they are trying to do to us.

If they actually wanted to kill as many infidels as possible, they wouldn't have anything to do with blowing up airplanes; they'd blow up backpack bombs in the lines at security checkpoints, where the same people who end up on planes are packed together and there's no security.

It has been pointed out elsewhere that bombs in relatively open areas (like check-in areas) tend to be a lot less effective than bombs in enclosed spaces (like aircraft), although some of the extra-large backpacks and suitcases could hold a much larger bomb than you could possibly smuggle onto an aircraft, and a bomb packed with lots of shrapnel can kill people in open spaces much more effectively than a straight explosive.

An effective check-in attack would probably involve detonating relatively small devices in the entrances to the check-in area so as to block exits simultaneously with large backpack shrapnel bombs further inside.

Sporting stadiums, however, are perhaps the ideal non-aircraft target, since there are limited exits to disable. You wouldn't even have to kill that many people directly - just detonate the exit-blocking devices first, then detonate the in-stands devices one-by-one so as to demonstrate a continuing threat - the crowd will take care of the rest by crushing people to death in the blocked exits.

Planes are pressurized, they would never implode, they would explode. Also, skydivers don't pressurize their planes, and they fly at lower altitudes than commercial jets, so it's not as big of a deal anyway.

You're right, but you're wrong. Sure, the O2 for the passengers is generated that way, but there are also O2 bottles stored in some of the overhead compartments for the use of cabin personnel, so that they can strap them on and assist passengers.

You owe the GP an apology.

(And if I hadn't already posted in this topic, I'd have probably modded you down.)

Actually, Occam's Razor states that the most parsimonious answer is probably correct, not the simplest. In other words, the answer which introduces the least new ideas and/or causes you to throw out the least old ideas, but which still fits the evidence. A little pedantic to point this out, I know, but it's not exactly the same as simplest.

The door does not need wind to keep it shut. Its mating surfaces are tapered just like a bathtub stopper, and the internal pressure holds the door tightly against the frame.

The door also does not just "open out". It starts by moving inward a couple of inches, which it can only do when the pressurization has been turned off and the pressure allowed to equalize. Then the upper and lower ends of the door bend inward a few inches, which reduces the total height of the door. Then it rotates slightly outward on a complex double pivot, which moves the forward edge a little aft and the aft edge a little forward. Now it's able to fit through the door frame, and it swings out on the same double pivot.

As for shooting a hole in the fuselage, that would have very little effect. An airplane is not a sealed pressure vessel; if it were, you'd be feeling really rotten halfway to Europe. The pressurization supplies a constant flow of air, and a unit called the outflow valve lets it out of the airplane at an electronically controlled rate to keep the correct pressure inside. If you shot four or five holes in the airplane with a.45, the outflow valve would just close down maybe halfway.

Now it would be possible to get a much bigger hole by shooting out a window, and that would cause a rapid -- not "explosive", but rapid -- decompression. The people near the window would undoubtedly lose their magazines -- but they wouldn't notice that, because the pilot would be doing some rather attention-getting maneuvers to get the airplane down to a safe breathing level.

public education of science is obviously in BIG trouble

See, this is why engineers get annoyed when computer engineers call themselves engineers...;-)

I'd like to second John's comments. He only has explored the trade space near realistic rocket fuels in depth; if you go outside it, there are whole categories of off the shelf, well known in the explosive industry explosive liquids.

TATP is about the dumbest possible route to a liquid explosive on a plane.

With any actual knowledge of explosives, any professional could come up with a few dozen easy options for alternate binary liquid explosives, or even pre-mixed liquid explosives which appear to be innocent sports drinks or sodas or wine or liquor, some of which could be safely drunk in moderate quantities to fool a security checkpoint guard into thinking it's a safe substance.

Several of these mixtures have no nitrogen whatsoever, and all of them have densities that don't alert the density-sensitive x-ray equipment.

Explosives experts have been quietly screaming at transportation security experts about this for years. Finally, once someone is caught trying it on a big scale, they listen.

From TFA: "Now we have news of the recent, supposedly real-world, terrorist plot to destroy commercial airplanes by smuggling onboard the benign precursors to a deadly explosive, and mixing up a batch of liquid death in the lavatories."

These guys actually blew up the bathroom in a plane with a cut down bomb for testing. After blowing up a movie theater seat.

Yeah, with nitroglycerin. The article from the Register said it was TATP, and proceded to explain his knowledge from researching TATP that it is highly unlikely TATP could be used to bring down a plane. TATP != nitroglycerin. And just looking up one aspect [scripps.edu] of the article seems to check out so far. The rest would be hard to check out without performing the experiments or talking to someone who has made it.

British media is obliged to lie by law. If it gives you the exact details it gets a call from the home office right away and may be sued for providing articles and materials useable for terrorism. It is quite funny actually. They do it all the time. For example in the docudrama about Smallpox BBC did after 9/11 there were 3-4 deliberate mistakes towards the end which were obviously introduced during last minute editing. As the docudrama has actually been written and shot with the assistance of a long list of virology and microbiology consultants there was no way for this to be non-deliberate.

Same with the 7/7 coverage. It took the media 3-4 days of speaking half truths to get to the point of what "household chemicals" were used in the process. Specifically, neither BBC, nor ITV mentioned the words paint thinner for 2 days. In fact, IIRC, BBC did not mention it till copycat explosions a few weeks later.

This is a result of the old antiterror laws passed by Tatcher to deal with IRA and there is nothing that can be done about it, because in Britain the freedom of speech is not enshrined in law.

As I do not want any visits from Tony Bliar govt henchmen I will follow that law and will not put any details here.

Disclaimer: I have not done any chemistry since I finished by degree 12 years ago. I have done an MSc in it though:-)

1. The plot is somewhat feasible.2. The media is focusing on the wrong type of explosives. It is not feasible to do that with peroxides and most organic explosives. It is perfectly feasible to do that with inorganics. Off the top of my head there are at least 3-4 very well behaved inorganic reactions which take two clear solutions and produce an explosive with 90%+ yield, nice, clean, no mess, no fuss, no fumes, no vapours, 5 minutes in the toilet and it is ready.3. While the chemical part of the plot is feasible, getting the chemicals on the plane is not. In all cases at least one of the solutions will look like a solid metal brick on X-ray (this should be enough for most slashdotters to guess one of the compounds) and is bound to cause undue interest even in the most apathetic security guard.